12/2019 EDIT: I conflated two bugs and incorrectly posted that this specific issue had been fully rectified. While it has been fixed for some users, others may still be seeing usage over-reporting.
Outdated posting
See this thread: FIX ISSUED: Over-reporting of Home Energy Notifications and Usage
We’ve issued a fix that should stop this from happening in the future, but are still working on a fix to historic stats for all users.
Watch the above thread, as updates will be posted there.